It’s because the alarm clock awoke you during REM SLEEP..............
How do you avoid waking up in REM sleep though? I had a sleep tracker app on my phone and saw that I snore and talked in my sleep. I recently learned that hitting the snooze somehow is bad for your health and I’ve done this for decades. Only recently when I’d wake up during the initial alarm I have multiple dreams and feel exhausted. I used to do thwe snooze thing but I wouldn’t feel exhausted but always enjoyed the extra sleep. I even set my clock time 30 minutes ahead just so I could do the 9 minute snooze thing a few times for that half hour.